The preparation of materials for pharmaceutical and medical use requires the utmost care. Such materials may be used for medication of humans or animals, as well as for various related purposes, such as the diagnosis of disorders of humans and animals.
If the materials deviate from the required quality standard, they may exert obnoxious or even fatal influence on the treated being or lead to equally dangerous wrong conclusions in for instance a diagnosis.
The preparation of such materials is entrusted to qualified pharmacists. They generate the materials in the required quality by using appropriate equipment and procedures in carefully constructed premises.
The materials, once prepared, must however be stored in containers in order to allow their transport to the application site. Between preparation and application, a considerable time interval may elapse. It is clear that the container must be such that no appreciable deterioration of the materials takes place.
Container systems for the purpose of storage of the materials have been elaborated in the past three or four decades for a very large number of applications. In many cases, the container system not only preserves the good quality of the packed material but additionally facilitates or even makes possible its actual application.
Many systems employ elastomeric (rubber) components, functioning practically always as a sealing means between the container content and the environment, and additionally also in many cases as a means for easy and/or safe application.
Two typical examples from a very large body are the following
1. A glass vial containing a fluid intended for parenteral medication is closed with a soft elastomeric stopper. The stopper allows penetration with a hypodermic needle or a spike. The sterile fluid may then be withdrawn from the vial without actually opening it, thus avoiding the danger of contamination with microorganisms or other undesirable matter.
2. A glass tube is used as a parenteral fluid cartridge by closing one end with an elastomeric stopper in the shape of a plunger. The other end is connected to a hypodermic needle. The fluid content of the cartridge can be pushed out through the needle by pushing the elastomeric plunger with a suitable plunger rod. In this application, the elastomeric part must form a static seal during shelf life of the cartridge and a dynamic seal during the actual application. In the latter stage, it must slide very smoothly in order to allow correct medical action.
From the above, it will be clear that elastomeric seals in this area may have a very wide variety of shapes and dimensions. In the following text they will be addressed as "elastomeric seals" for short.
In the course of the last three decades, much work has been devoted to the development of suitable materials for elastomeric seals in this field. The work was complex because elastomeric materials for the production of seals are composed themselves over a number of starting materials. Such starting materials must be most carefully selected as well as combined in accurately balanced ratios in order to obtain seals possessing a complex of properties required for the application.
Said seals having
the ability to form a static, and if required, dynamic gas- and liquidtight seal for a container containing pharmaceutical or medical preparation (1),
very low, and indeed pharmaceutically acceptable, release of extraneous material to the pharmaceutical or medical preparation (2), and
durability or persistence of the required properties during the storage time of the container with a pharmaceutical or medical preparation (3),
must additionally have, in order to be suitable to be used in equipment for filling or closing containers, the following properties
ability to support currently practiced technical treatments for surface cleaning and sterilization (4), and
ability to be processed in current technical container filling and closing equipment (5).
By selecting suitable elastomeric base materials and further components, compounds may be obtained which, after curing in an appropriate shaping treatment, have a good balance of properties (1), (2) and (3). Such compounds are proprietary to the pharmaceutical rubber industry.
It has been observed that their final processing, especially on a large scale, in fast running modern machines, requires a certain adaptation of their surface state. By their nature, elastomeric objects have a relatively high coefficient of friction, for instance 2.4. This hampers their ability to be transported in filling equipment and similar machinery and, as a consequence, such equipment must be adapted in complicated and mostly costly ways.
In order to overcome this problem, the elastomeric seals in many cases are coated with some lubricant, for instance silicone oil. Such treatment is additionally favorable in preventing the seals from sticking to one another, which also is a frequently observed phenomenon in uncoated seals, especially after treatment in cleaning, cleansing, sterilization and drying equipment.
However, the silicone oil or other lubricant spoils some desirable properties of the seals as an extraneous material, it contaminates the pharmaceutical or medical material stored in the container. In the case of silicone oil, for instance, it has been observed that a water-based medical preparation after contact with the silicone oil treated elastomeric seal, contains a relatively large quantity of silicone oil droplets in emulsified state.
Coatings with various materials have been proposed, but they generally involve the already mentioned or other drawbacks, for instance a decreased sealing capacity or a high application cost.
The present invention purports to resolve the problem by applying a relatively simple and at the same time cost-efficient treatment, consisting of introducing in a carefully controlled way an amount of halogen atoms into the seal surface. The treated seals acquire the necessary low friction coefficient and lose their aggregation tendency, even upon stringent cleaning, cleansing, sterilizing and drying treatment. They do not lose the desirable properties they already possess before the treatment and release a very low amount of extraneous material to a pharmaceutical or medical preparation.